Field of the Invention
Starter having a reduction gear mechanism disposed between a starter motor shaft and a pinion and, more particularly, to a reduction starter in which the motor shaft and the shaft carrying the pinion are coaxially arranged.
A typical conventional starter for automotive engine has a pinion carried by the shaft of a starter motor which, when required, is adapted to be brought, when required, into engagement with a ring gear provided on the outer peripheral surface of a flywheel of the engine.
In recent years, a new type of starter called as "reduction starter" has been put into practical use in order to obtain a good starting performance. However, disadvantages of these proposed reduction starters reside in the fact that a reduction gear mechanism is constituted by spur gears and, thus, the motor shaft and the pinion shaft are not disposed coaxially but arranged parallel at a distance from each other. Consequently, the construction of the proposed starters, as a whole, is complicated resulting not only in an increase the size thereof but also in the manufacturing cost.
In order to eliminate the disadvantages of the conventional reduction starter attributable to the use of the spur gears, a reduction starter employing a planetary reduction gear mechanism has been proposed in, for example, the specification of British Pat. No. 964,675. In this type of reduction starter, it is possible to arrange the pinion shaft coaxially with the motor shaft, so that the size of the reduction gear mechanism can be reduced considerably. Consequently, the size of the reduction starter can be substantially as small as that of the conventional starter in which the pinion is connected directly to the motor shaft.
The reduction starter having the planetary gear type reduction mechanism, however, still suffers from the problem of high production cost due to a high precision required in the fabrication and assembling of the planetary gear type reduction gear mechanism. As is well known, any planetary gear mechanism is required to use a plurality of planet gears for attaining a good balance of mass and a high torque-transmitting performance. These planet gears have to be fabricated and mounted with a high precision in order to avoid local or uneven contact between gear teeth which would seriously lower the performance and durability of the gears. Accordingly, an object of the invention is to provide a reduction starter having a planetary gear type reduction gear mechanism improved to satisfy both of the demands for low cost and high performance to thereby overcome the above-described disadvantages of the prior art.
In accordance with advantageous features of the present invention a reduction starter is provided which employs a planetary gear type reduction mechanism having an outer ring gear displaceable, within a predetermined limit, in directions perpendicular to an axis common to a central sun gear and an output shaft which carries planet gears for rotation about the common axis.
The above and other objects, features and advantages of the invention will become clear from the following description with reference to the accompanying drawings.